Heat exchanger

ABSTRACT

A heat exchanger includes at least two tube sections wound helically to form a spiral and are arranged in an interlacing manner inside one another for guiding a heat transfer fluid. The heat exchanger includes a first tube section helically wound to form a first spiral. The first tube section is for guiding a first heat transfer fluid and a second tube section is helically wound to form a second spiral, the first spiral and the second spiral being arranged in an interlacing manner inside one another and being connected to one another.

The present invention relates to a heat exchanger comprising a tube section which is wound helically to form a spiral. Such a heat exchanger is known from U.S. Pat. No. 5,502,829. In this known heat exchanger the spiral serves to guide a coolant as a first heat transfer fluid and is arranged in a flow duct surrounded by an elongated housing, through which with the aid of a fan air is conveyed as a second heat transfer fluid.

One problem of this known heat exchanger is that the spiral impedes the air flow only on a part of the cross-section of the flow duct. In the free inside of the spiral and possibly also between the outside of the spiral and the housing higher flow velocities are produced than in the immediate vicinity of the spiral so that a large quantity of air passes the heat exchanger without coming into closer thermal contact with the spirals. Other parts of the airflow pass in succession along many windings of the spiral and, in doing so, heat up intensely, so the efficiency of the heat exchange decreases sharply toward the downstream end of the flow duct.

A more compact heat exchanger than the aforementioned one is described in U.S. Pat. No. 3,524,329. In this heat exchanger, the tube which guides the coolant forms spirals, which are connected to one another in series and alternately exhibit a left-hand and right-hand direction of rotation, in a plurality of planes oriented perpendicularly to the direction of flow of air through the heat exchanger. The production of this heat exchanger is, however, substantially more costly than that of the first-mentioned heat exchanger, as it is not possible to wind the tube continuously onto one winding core.

A compact heat exchanger with spiral-shaped tube sections, through which the coolant flows in series, is also disclosed in DE-OS 2 136 369. This known heat exchanger is formed from a tape wound into a spiral fitted with coolant ducts.

The object of the present invention is to indicate a compact, easily implementable heat exchanger and a method for the production thereof.

The object is achieved firstly in a heat exchanger comprising a first tube section which is wound helically to form a first spiral for guiding a first heat transfer fluid, in which the first spiral and a second spiral which is wound from a helically wound second tube section are arranged in an interlacing manner inside one another and, in flow engineering terms, are connected to one another.

The object is achieved secondly in a method for the production of the heat exchanger defined above, in which a tube is wound around a first winding core so as to form the first spiral, a slotted second winding core, through the at least one slot of which the inlet and outlet of the spiral can pass, is placed around the first spiral, and from the same tube a second spiral surrounding the first spiral is wound on the second winding core.

The tube sections of the two spirals are preferably connected to one another in one piece, in flow engineering terms, to form a continuous spiral.

In order to avoid a sharp kink in the tube at the transition from the first to the second spiral, the two spirals are preferably wound with opposing handednesses. In this case, the tube sections of the two spirals are also preferably connected to one another at a same end of the two spirals respectively.

Alternatively, the tube sections of the two spirals can also be connected by means of a tube section which extends between opposite ends of the two spirals. In this case, the handedness of the two spirals can be the same.

Furthermore, a third or yet further spirals can be provided, which are respectively interlaced with the first and the second spiral.

Production of the heat exchanger is particularly simple if the spirals running into one another have a constant cross-section in the longitudinal direction such that the spirals are shaped e.g. in the form of a circular cylinder or a rectangular prism.

In order to improve the efficiency of the heat exchanger, it may be desirable for the spirals arranged in an interlacing manner inside one another to have a cross-section that tapers in the longitudinal direction, e.g. like a truncated cone.

A free space in the inside of the innermost spiral can be utilized by arranging an evaporation tray or a dryer there.

Further features and advantages of the invention will emerge from the description below of exemplary embodiments with reference to the attached drawings, in which:

FIG. 1 shows a perspective view of a heat exchanger according to a first embodiment of the invention;

FIG. 2 shows a plan view of the heat exchanger from FIG. 1 in an axial direction;

FIG. 3 shows a perspective view of a modified embodiment of the heat exchanger from FIG. 1;

FIG. 4 shows a perspective view of a third embodiment of the heat exchanger;

FIG. 5 shows an axial section through a fourth embodiment of the heat exchanger;

FIGS. 6 to 11 show stages in the production of the heat exchanger according to the invention; and

FIG. 12 shows a stage in the production as per FIG. 10 of the heat exchanger from FIG. 4.

The heat exchanger shown in FIG. 1 comprises three spirals 1, 2, 3 formed continuously in one piece from a metal tube formed in the manner of a helical spring, which in the present exemplary embodiment run into one another coaxially relative to a longitudinal center axis M and are in this way arranged very compactly in an interlaced and thus space-saving manner. The spirals 1, 2, 3 shown each have five windings so as to keep the drawing clear; in practice, the number of windings is generally larger such that the dimension of the heat exchanger along the longitudinal center axis M is greater than it is perpendicular thereto.

The spirals 1, 2, 3 are surrounded by a housing 4 shown in a cut-open manner in the figure, which housing serves to keep an airflow passing along the spirals 1, 2, 3 concentrated. Anchored to the housing via four braces 5, of which only two are visible in the figure, is a fan which serves to drive the airflow through the housing 4. A propeller (not visible in the figure) of the fan is located on the open rear side, facing away from the observer, of the housing 4. A motor 6 of the fan is arranged in an inner cavity of the innermost spiral 1 and consequently represents a flow obstacle which forces the airflow running through the housing to pass closely along the spirals 1, 2, 3.

An intake terminal for coolant is labeled 7. From this intake terminal 7 the coolant reaches firstly the inner spiral 1 which has a right-hand direction of rotation. A tube section 8 forms a transition to the central left-handed spiral 2. A corresponding transition from the spiral 2 to the outer, again right-handed, spiral 3 is located on the side of the heat exchanger facing away from the observer and is not visible in the figure. The coolant exits the heat exchanger via an outlet terminal 9.

To illustrate the structure of the heat exchanger, FIG. 2 shows a plan view of the three spirals 1, 2, 3 parallel to the longitudinal center axis M. The tube section 10, which connects the spirals 2 and 3 to one another at the end of the arrangement facing away from the observer, can also be seen in this plan view.

A second embodiment of the heat exchanger is shown in FIG. 3, the housing of this embodiment, which does not differ from that of the first embodiment, being omitted from the figure. Here, a flat tray 11 is located on the inside of the innermost spiral 1. If the heat exchanger is integrated in a cooling device, the tray 11 serves as an evaporation tray, i.e. it collects condensation water which flows out from an evaporator of the cooling device, and vaporizes this with the aid of the airflow running through the heat exchanger. In this embodiment it is not therefore necessary to block the interior of the inner spiral 1 with a fan motor or such like. Where the spirals are sufficiently long, however, there may be ample space in the cavity of the inner spiral both for the fan motor and for the tray 11.

In place of the tray 11 or possibly also together with this tray, a dryer for the coolant connected in series to the spirals 1, 2, 3 can be accommodated inside the spiral 1.

In the diagram in FIG. 3, an air gap is located under the base of the tray 1 between the base of the tray 11 and lower straight-line sections 12 of the inner spiral running thereunder such that air can flow around the lower sections 12 over their entire periphery. Alternatively, the tray 11 could also be fastened directly to these lower sections 12 such that these can emit the heat of the coolant flowing through them via the fastening direct to the tray 11.

Interlaced spirals 1, 2, 3 according to a third embodiment of the inventive heat exchanger are shown in FIG. 4. In this embodiment all the spirals 1, 2, 3 have the same direction of rotation and the spirals are connected to one another respectively by means of a tube section 13 or 14 running approximately axially which extends in an essentially axial direction in an interspace between two spirals 1, 2 and 2, 3 from one end of the heat exchanger to the other. The direction of flow of the coolant relative to the longitudinal center axis M is the same here in all three spirals 1, 2, 3. That is, when air flows through the heat exchanger in the direction of the arrow P and the terminals 7 and 9, as in the first embodiment, function as an inlet and outlet terminal respectively, all three spirals 1, 2, 3 operate on the countercurrent principle.

The tube sections 13, 14 in this embodiment can also fulfill a stabilizing function for the spiral arrangement by being fastened, optionally via a thermally insulating intermediate layer, to the windings of one of the two spirals between which they extend, or even to both spirals.

FIG. 5 shows an axial section through the spirals of a heat exchanger according to a fourth embodiment of the invention, sections of the spirals lying above the section plane being shown as dotted outlines respectively. The spirals 1, 2 run here on conical surfaces, i.e. the diameter of their windings decreases from one longitudinal end of the heat exchanger to the other. The advantage of this arrangement is that when air flows parallel to the longitudinal center axis through the spirals, air which has not yet already been preheated on a different winding flows against all the windings, including those at the downstream end of the heat exchanger.

A method for the production of the heat exchanger according to the invention will be explained with reference to FIGS. 6 to 11.

FIG. 6 shows a cylindrical winding core 15 and a delivery roll 16 of a thin-walled metal tube made e.g. of copper. A free end of the metal tube is temporarily fixed to the surface of the winding core 15. Simultaneously rotating the winding core 15 and displacing the delivery roll 16 along the winding core 15, unwinds the metal tube from the delivery roll 16 and winds it in evenly spaced windings onto the winding core 15, as shown in FIG. 7. This is how the spiral 1 is obtained.

Once the spiral 1 has been generated fully, a second winding core 17 in the form of a longitudinally slotted sleeve is pushed in an axial direction on to the first winding core 15 and the spiral 1, the free end of the tube protruding through the slot 18, as can be seen in FIG. 8.

When in the stage shown in FIG. 9 the second winding core 17 is pushed fully onto the first winding core 15, the tube section 8 which connects the spiral 1 to the delivery roll 16, also extends through the slot 17.

Both winding cores 15, 17 are now rotated together, and at the same time the delivery roll 16 is displaced along the winding cores 15, 17 back to its starting position. The second spiral 2 is obtained in this way, as can be seen in FIG. 10.

Now, as shown in FIG. 11, a third, likewise slotted, winding core 19 is pushed on to the winding cores 15, 17 and the spirals 1, 2, the free end of the tube and the tube section 10 in turn extending through the slot 20 of the winding core 19. Rotating the winding cores and displacing the delivery roll 19 now generates the spiral 3 on the winding core 19. Since this process proceeds in the same manner as the winding of the spirals 1 and 2, it is no longer shown in the figures. It is obvious that the number of winding cores and of spirals generated thereon can in principle be increased to any number as required.

When the desired number of spirals has been generated, the temporary fastening of the tube to the inner spiral 15 is detached, and the winding cores are extracted.

The production of a heat exchanger of the type shown in FIG. 4 proceeds up to the stage shown in FIG. 9 precisely as described above. Now, however, instead of immediately starting to wind the spiral 2 with opposing handedness, as shown in FIG. 10, the tube, as shown in FIG. 12, in the slot 18 of the winding core 17 is retracted over the whole length of the spiral 1 so as to form the section 13 described with reference to FIG. 4, and the spiral 2 is then wound with the same handedness as the spiral 1. The same procedure is followed with all further spirals. 

1-11. (canceled)
 12. A heat exchanger comprising: a first tube section helically wound to form a first spiral, the first tube section for guiding a first heat transfer fluid; and a second tube section helically wound to form a second spiral, the first spiral and the second spiral being arranged in an interlacing manner inside one another and being connected to one another.
 13. The heat exchanger as claimed in claim 12, wherein the first tube section and the second tube section are connected in one piece.
 14. The heat exchanger as claimed in claim 13, wherein the first tube section has a handedness in a one direction and the second tube section has a handedness opposite to the handedness of the first tube section.
 15. The heat exchanger as claimed in claim 13, wherein the first spiral has an end, the second spiral has an end that coincides with the end of the first spiral, and the first tube section and the second tube section are connected to one another at the coinciding ends of the first spiral and the second spiral.
 16. The heat exchanger as claimed in claim 13, wherein the first tube section and the second tube section are connected via an extension of one from the group of the first tube section and the second tube section that extends between opposite ends of the first spiral and the second spiral.
 17. The heat exchanger as claimed in claim 12 and further comprising at least one third spiral interlaced with the first spiral and the second spiral.
 18. The heat exchanger as claimed in claim 12, wherein the first spiral and the second spiral are interlaced concentrically.
 19. The heat exchanger as claimed in claim 12, wherein the first spiral and the second spiral each has a constant cross-section in the longitudinal direction.
 20. The heat exchanger as claimed in claim 12, wherein the first spiral and the second spiral each has a tapering cross-section in the longitudinal direction.
 21. The heat exchanger as claimed in claim 12 and further comprising one from the group of an evaporation tray and a dryer arranged inside the innermost spiral of the first spiral and the second spiral.
 22. A method for the production of a heat exchanger, the method comprising: winding a tube around a first winding core to thereby form a first spiral; placing a slotted second winding core around the first spiral; and from the tube, winding a second spiral on the second winding core in a manner resulting in the second spiral surrounding the first spiral. 